Monterey County, CA Accessory Structures: ADU Rules (2026)

Monterey County's ADU rules implement state ADU law (Cal. Gov. Code section 65852.2 and successor section 66323, effective 1/1/2025) through MCC section 21.64.030 (inland zoning) and MCC section 20.64.300 (coastal zoning). Maximum ADU size is 1,200 sq ft (or 850 sq ft for studio/one-bedroom on lots without a primary unit, per state law); maximum JADU size is 500 sq ft and must be within or attached to the primary single-family dwelling. Inland ADUs are ministerially permitted with no discretionary review, no owner-occupancy requirement (for permits applied for between 1/1/2020 and 1/1/2025; check current status), and minimal parking requirements (no parking required within 1/2 mile of transit). In the Coastal Zone, ADUs require a Coastal Administrative Permit; the Board of Supervisors approved an expanded coastal ADU ordinance on November 18, 2025, following Coastal Commission certification, allowing more ADUs in Big Sur, Carmel Highlands, and other coastal areas subject to ESHA, hazard, and visual-resource protection. Setbacks are minimal (4 ft side and rear), height is generally 16-25 ft depending on configuration, and short-term rental of an ADU is restricted (the County's vacation rental ordinance allows Homestays but prohibits Commercial Vacation Rentals in Big Sur, Carmel Highlands, Moss Landing, and Carmel Valley residential zones).